问题
选择题
Li Ning was able to set up a school for gymnasts in 1991, ______ he has continued to help young people to achieve their sporting ambitions.
A．when
B．dring which
C．since then
D．since when
答案
答案：D
题目分析：考查非限制性定语从句。句意：1991年，李宁为体操运动员修建了一个学校，从那以后，他一直继续帮助年轻人实现他们的体育梦。句中有逗号，是非限制性定语从句，during which=when，since then不能引导定语从句，排除A、B、C。since when从那以后，符合题意。故选D。